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Motorized Bicycle General Discussion All topics regarding bicycles with engines.

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  #1891  
Old 08-01-2011, 11:54 AM
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Default Re: what did you do to your motor bike today?

Got the darn sheared front mount bolts drilled out from the SBP universal mount... Thank goodness for left handed twist cobalt drill bits from Snap On tools, they make life a whole lot easier one just spun out with the drill twist and the other backed out easily with an EZ out. Put in m6x1 20mm long stainless hex heads.

Time to go for a ride after I put some NeoSporin on the burn it gave me from the head touching my calf when they sheared.
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  #1892  
Old 08-01-2011, 12:03 PM
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Default Re: what did you do to your motor bike today?

Quote:
Originally Posted by MarkSumpter View Post
Got the darn sheared front mount bolts drilled out from the SBP universal mount... Thank goodness for left handed twist cobalt drill bits from Snap On tools, they make life a whole lot easier one just spun out with the drill twist and the other backed out easily with an EZ out. Put in m6x1 20mm long stainless hex heads.

Time to go for a ride after I put some NeoSporin on the burn it gave me from the head touching my calf when they sheared.
Quote:
Originally Posted by Creative Engineering View Post
Hello all,

I've been reading through some of the recent posts and saw some interesting comments regarding the fasteners that the chinese use to assemble their engines.

I've also read a few posts about the alternatives; Grade 8, Grade 5, even stainless.

Stainless is not a good choice for most applications...Stainless offers very little holding strength. Stainless is malleable...it will not take torque.

Stainless fasteners are used for finishing, and required, in applications where food items come in contact with machinery.

Stainless fasteners share the same stigma as titanium...most people think that titanium is lighter than aluminum and stronger than steel when in fact titanium sits nearly in the middle. Titanium is heavier than aluminum, lighter than steel: stronger than aluminum, not as strong as steel.

A lot of people also wrongly assume that stainless fasteners are the ultimate..."they are for the right application". They are more expensive, so the notion is that they must be better...just remember "better for what". Engine powered bikes need tough fasteners... unless you are seeking FDA approval leave the stainless out...lol.

The exception; dress-up items...stainless fasteners are fine for decoration.

DO NOT MIX STAINLESS WITH ALUMINUM...especially cast aluminum where heat is involved. Over time the materials will bond together making removal impossible. Wring them off and drill them out...so much fun!

The notion that grade "8" is too brittle and will prematurely fracture is also wrong. Grade "8" fasteners are made from chrome moly, (4130, 4140), heat treated to Rockwell 38-42 with a tensile strength of 140 to 190 PSI depending upon alloy and rockwell hardness.

Grade "8" fasteners are used throughout the racing world!

Grade 5 fasteners are fine as replacements for any of the hardware on the Chinese engines.

Chinese hardware...cheap, saw cut, all-thread for studs. All-thread never has been "high grade", it was manufactured as a temporary battle field "fix-it" during world war one. Cut off what you need and you have an instant bolt. The process of making all thread guarantees a low tensile stength product suited for emergency use...just as intended.

I use grade "8" allens for almost eveything, simply for the ease. I prefer an allen wrench to a screwdriver.

Jim
Did not know if you knew the Stainless will be weaker?
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  #1893  
Old 08-01-2011, 01:16 PM
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Default Re: what did you do to your motor bike today?

Killer, Bummer! Fixable?

On the studs thing, when I do replace em, (which I rarely do. More out of lazy) I use the automotive ones. Any thoughts on them? They cost a lot and more wondering if it is just over kill. Have never had any fail though.
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  #1894  
Old 08-01-2011, 03:04 PM
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Default Re: what did you do to your motor bike today?

In reference to Creative Engineering's entry of "DO NOT MIX STAINLESS WITH ALUMINUM...especially cast aluminum where heat is involved. Over time the materials will bond together making removal impossible. Wring them off and drill them out...so much fun!"

Stainless also being a dissimilar metal that aluminum will create a galvanic effect (read battery effect) when in close contact with aluminum. Threaded into a hole of aluminum is a recipe for disaster when heat and moisture are present. The threads will start to corrode in the aluminum as it is a softer metal than stainless thusly weakening them.
The stainless will also pit a little and the resulting oxides that form in between the pitted stainless and corroded aluminum will effectively create a "super loc-tite" effect.

Oil or grease can slow this reaction down a little, but not stop it. The best I know of is simply to use milk of magnesia. That's right, the stuff that is sold in the medecine section for bowl problems. The magnesium will act like a sacrificial metal and stop the corrosion between the stainless and aluminum. The magnesium will break down very slowly. It will not act like a loc-tite. It will not cause the threaded parts to come loose any easier than if assembled dry.

Shake the bottle up very well, pour a little into a cup and dip the threads of the bolt or stud into the milk of magnesia before threading them into the aluminum.
Wipe off any extra that gets squished out.
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  #1895  
Old 08-01-2011, 03:23 PM
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Default Re: what did you do to your motor bike today?

REALLY a difference in the quality of Snap-On tools and the china junk that I use now...

lol I stuck one drill bit in a piece of mild steel and darn near straightened the bit out to a single blade! It was hilarious!

Gosh those offshore boats are awesome! Would have liked to see something like that. Maybe one day...
rc
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  #1896  
Old 08-01-2011, 06:00 PM
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Default Re: what did you do to your motor bike today?

Galvanic effect aside (which is negligible in stainless to aluminum mating surfaces) the use of stainless in mounting an engine is preferred for the simple fact of its malleability and that it can actually give with the stress of the engine where grade 8 with a higher RF will shear and there is a neat little product out there called anti-seize to keep down aluminum oxide from forming between the threads. Not my first rodeo folks I have used this same method for years with good success.
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  #1897  
Old 08-01-2011, 06:27 PM
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Default Re: what did you do to your motor bike today?

Got sick of redoing my HF 79cc pull starter spring. Put a Predator 99cc pull start on it. Bolted right on. Don't "feel" right but the grip is much more comfortable and more importantly worked.

Does look way better with a black cover too. (I hate the greyhound blue)
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  #1898  
Old 08-01-2011, 09:25 PM
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Default Re: what did you do to your motor bike today?

Then why has ever outboard engine I've ever seen use stainless steel screws into cast aluminum?
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  #1899  
Old 08-02-2011, 01:59 AM
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Default Re: what did you do to your motor bike today?

today I think I fixed the carburetor choke lever on my old NT. It was getting loose and it would fall down just sitting there. I was wondering why I could not get any power (DOH!) I hope this will fix my woes. If not that than I may have to get a new spark plug my current one it getting a little thin I think.


Mike
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  #1900  
Old 08-02-2011, 03:21 AM
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Default Re: what did you do to your motor bike today?

Quote:
Originally Posted by Mike B View Post
Then why has ever outboard engine I've ever seen use stainless steel screws into cast aluminum?
Finish durability and the factory can apply any suitable anti-seize or anti corrosion product on the threads as they please during assembly.
Some factories don't care and if it buggers up in a few years, then the service department of the dealership makes more $ fixing it. Dealerships like certain designed in failures.
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Does not come with a fortune cookie."
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